The necessity of visibly demonstrating the solidarity of the Allies and of their willingness to act together rapidly exercised the minds of the military members of the original Western European Union. Proposals were made for integrated European units, brigades and formations. Unfortunately, the practical difficulties seemed too great and ideas were abandoned. Once the NATO Treaty had been signed, headquarters were formed, but below that level, corps and divisions remained national. In early 1960 General Lauris Norstad, then Supreme Commander Allied Powers Europe, decided to set up a working party to define the organization of an international headquarters and a multinational brigade-sized formation that would become SACEUR’s own mobile task force. The recommendations of this working party were accepted by SACEUR and the Military Council and so, in March 1960, the Allied Command Europe Mobile Force (AMF) came into being. Its purpose was to make clear to any actual or potential aggressor that an attack against one nation would constitute an attack against all members of the Alliance, demonstrating the unity of purpose upon which NATO is founded. The NATO Force Structure (NFS) has changed substantially over the last 30 years.
In the Cold War it was characterized by a large standing force with smaller reaction forces configured for strategic confrontation and potential large-scale conflict with the Soviet Union. In the post-Cold-War period, the NFS shifted to a pool of forces, at various levels of readiness, forces generated and organized in response to non-specific crises or conflicts. In such circumstances, it was envisaged that the NATO force would be organized, at the time of the crisis, to meet the agreed political and military objectives.
Following the tragic events of September 11, 2001, and the subsequent invocation of Article 5 of the Washington Treaty during the Prague Summit in 2002, NATO members endorsed a comprehensive set of measures. These measures were designed to enhance the alliance's capacity to address security challenges affecting its forces, populations, and territory. The decisions taken aimed at providing NATO with well-balanced and effective capabilities, enabling the alliance to undertake a diverse range of missions and collectively respond to various threats, including terrorism and the proliferation of weapons of mass destruction. Recognizing the importance of effective military forces as part of their overall political strategy, NATO members announced the establishment of the NATO Response Force (NRF). This force, comprising approximately 40,000 troops drawn from selected elements of Allies’ force structures on a rotational basis, is required to be technologically advanced, flexible, deployable, interoperable, and sustainable, covering land, sea, and air components. The NRF swiftly assumed a crucial role in various global events, demonstrating its versatility and effectiveness. In 2004, elements of the NRF contributed to securing the Summer Olympics in Athens and supported the Afghan presidential elections. In 2005, NRF aircraft delivered relief supplies to the United States after Hurricane Katrina, demonstrating its capability for disaster response. Subsequently, from October 2005 to February 2006, the NRF was active in providing disaster relief in Pakistan following a severe earthquake, involving the transportation of supplies and deployment of personnel to assist in the relief efforts. Since 2014 and following the Russian invasion of Crimea, with the Wales Summit, NATO has developed Graduated Response Plans (GRPs), which have led to an adjustment to the NRF structure. The GRPs also linked the NRF force package with specific advance plans for regional deployment within SACEUR's Area of Responsibility (AOR). During this period, Allies' national forces have also undergone significant change, characterized by: strengthening in-place national forces; new deployments collectively by the Alliance and individually by Allies in support of national and regional defense; the modernization of equipment and forces; and the establishment of new NFS regional HQs. The enhanced NRF (eNRF) further improved NATO's deterrence and defense posture by developing the original NRF model into three echelons of graduated readiness: the Very High Readiness Joint Task Force (VJTF), the Initial Follow-on Forces Group (IFFG) and the Follow-on Forces Group (FFG). The NATO Readiness Initiative (NRI), introduced in 2018, was developed to strengthen and improve readiness, by defining clear and ambitious readiness targets.